Cobalt nanostructures have been prepared by a chemical route based on the Co(II) reduction inthe confined space of cobalt bis(2-ethylhexyl)sulfosuccinate (Co(DEHSS)2) reverse micellesdispersed in n-heptane. This procedure involves the rapid formation of surfactant softly coatedCo nanostructures followed by a slow separation process of the magnetic-field responsiveCo/surfactant nanocomposites from the liquid phase. The detailed structure of thin films of theCo/surfactant nanocomposites has been investigated by scanning force microscopy (SFM). Thethin films were characterized by different anisotropic features. Micrometric long domains ofself-aligned ellipsoidal NPs (tens of nanometers in size) have been observed, together withbendable micrometric long homogeneous nanofibers (NFs). The film structures were stronglydependent on the Co/surfactant ratio and, by increasing the Co percentage, the system wasforced towards the formation of mutually connected superstructures consisting of anisotropicbands of self-aligned NFs and anisotropic 2D close packed Co-NP super-lattices.Transmission electron microscopy (TEM) showed that the NPs observed by SFM are ineffect composed of almost spherical and oxygen-free cobalt nanoparticles, 1–3 nm in size,which typically assemble in larger ellipsoidal systems tens of nanometers in size. Magneticforce microscopy (MFM) demonstrates the magnetic response of these thin films, highlightingthe different behavior (attractive/repulsive) of the Co-NPs aggregates towards the oscillatingmagnetized tip. The above structural findings have been interpreted in terms ofnanostructures/matrix interaction along with a fine balance between short-range isotropicrepulsions, van der Waals attractions and long-range anisotropic magnetic interactions.
|Numero di pagine||10|
|Stato di pubblicazione||Published - 2009|
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering
- Electrical and Electronic Engineering